Tag: dark energy

A composite image of the star cluster 47 Tucanae,
taken by the Dark Energy Camera

We know that the universe is expanding, and that it’s doing so faster and faster. But we don’t know why the rate of expansion is increasing. Astronomers have dubbed the unknown cause “dark energy,” which is a pretty cool name for something we know absolutely nothing about. To shine some light on the mystery, scientists devised a the most powerful digital camera in the world: the Dark Energy Camera, capable of seeing 8 billion light years into space. And after eight years of development, last week the camera captured its first images.

Note: You may want to click the full-screen button down there and watch this in its full hi-def glory.

Ever wished you could float through space, drifting past stars and cosmic dust clouds? The largest-ever 3D map of the universe, shown in the video above, gives you a sense of what that might be like, though the bright dots surrounding you are not stars, but whole galaxies, and you’re not quite drifting, but ripping along at a quadrillion times the speed of light.

To get a sense of the speed, just look at those galaxies and remind yourself that each is home to hundreds of billions of stars like our own. And you can even see, as the video progresses, the distinctive soap-bubble arrangement of the universe’s galaxies, arrayed in closely packed groups around vast tracts of empty space.

The Sloan Digital Sky Survey produced the 3D map from newly released data collected during two years of a six-year project. Knowing the locations of over a million galaxies will help astronomers find out how dark matter and dark energy are affecting the visible universe.

In the meantime, we’ll just watch this video again. And again. And again.

To get a better handle on these “dark” forces, which we can’t detect with our puny human equipment, researchers Christian Marinoni and graduate student Adeline Buzzi from the University of Provence used an approach that’s actually been around longer than the idea of dark energy–a 1979 theory from Charles Alcock.

Its multicolored ovals have become some of the most distinguishable pictures in science. Its estimate of the age of the universe is the most accurate ever produced. Its science team ought to win the Nobel Prize for Physics, Nobel predictors at Thomson Reuters say. But now, after nine years in space, the accomplished Wilkinson Microwave Anisotropy Probe (WMAP) is headed for its retirement home.

The spinning WMAP satellite scanned the sky to measure tiny variations in the temperature of the cosmic microwave background radiation 380,000 years after the Big Bang. Scientists consider the CMB the first light from the young universe after matter and light could exist independently as the universe cooled. Only sensitive microwave space telescopes can detect the temperature fluctuations, which amount to just a millionth of a degree against an average backdrop of less than -450 degrees Fahrenheit. [Spaceflight Now]

One of the top three priorities for the next decade of astrophysics and astronomy, we noted this week, is unraveling dark energy, the weird force that pushes the universe apart. Given that scientists know next-to-nothing about dark energy—besides the fact that it makes up most of the universe—any step could be an important one. Thanks to a study out this week in Science, astrophysicists at least can have more confidence in this phenomenon that can’t be directly seen or measured: Their estimates for dark matter’s extent appear to be on target.

The technique scientists used in this study is called gravitational lensing, and the lens in this case is a huge galactic cluster called Abell 1689.

Because of its huge mass, the cluster acts as a cosmic magnifying glass, causing light to bend around it. The way in which light is distorted by this cosmic lens depends on three factors: how far away the distant object is; the mass of Abell 1689; and the distribution of dark energy [BBC News].

There is a lot of space to explore and a limited amount of money to spend. So every ten years the National Research Council’s “Decadal Survey” recommends which astronomy and astrophysics projects should get first dibs. Last week, the committee released their recommendations for 2012 through 2021. The projects that got the thumbs-up from astronomers would tackle big tasks, like hunting for dark energy and seeking out new exoplanets.

Though funding agencies (like NASA, the National Science Foundation, and the Department of Energy), Congressional committees, and the scientific community often use the survey to select the observatories on which to focus attention and resources, some were skeptical about this report given the 2001 survey’s recommendations and results.

Although these reports have always been influential—policymakers like scientists to rank their needs—only two of the seven major projects that appeared on the wish list in the 2001 survey have been funded, leading astronomers to wonder if the exercise is as useful as they’d like it to be. Previous surveys have also been faulted for providing unrealistic cost estimates, as low as a fifth of what certain missions have ended up costing. As a result, there has been considerable pressure on the committee that authored [Friday’s] report to prioritize projects more effectively and estimate costs better. [Science Insider]

The theory of general relativity: It works. OK, it’s not exactly Earth-shattering news that Albert Einstein’s century-old idea works in real life. That’s been shown over and over. But what had been difficult for researchers to do until now was verify the theory on truly massive scales beyond the solar system, that of whole galaxies and clusters of galaxies. This week in Nature, Reinabelle Reyes and colleagues report that they did it, and that Einstein was proven correct once more.

While the find is a nice coup for Reyes’ team, its importance goes beyond just reaffirming the great scientists of yesteryear with yet another “Einstein was right” story. The existence of dark matter and dark energy is based on the assumption that Einstein’s gravity is affecting galaxies billions of light-years from Earth in the same way that it affects objects in our solar system [National Geographic]. However, if the study had shown that general relativity needed a slight adjustment at vast distances (like the nudge Einstein himself provided to Newton’s physics), that could have altered prevailing ideas about dark matter and energy. This research indicates those pesky ideas may be here to stay [Space.com].

The mysterious force known as dark energy that is causing the universe’s expansion to accelerate is also preventing galaxy clusters from getting too big for their britches, a new study suggests. The existence of dark energy was first proposed a decade ago but the stuff has never been directly detected, and there’s much we don’t know about it. However, all the indirect studies have agreed that it acts like a kind of anti-gravity: A repulsive force that permeates empty space and, bizarrely, grows stronger with distance, precisely the opposite of what happens with gravity [Washington Post].

In the new study, researchers used NASA’s orbiting Chandra X-ray observatory to examine the growth patterns of galaxy clusters. After bulking up rapidly in the first 10 billion years of cosmic time, clusters of galaxies, the cloudlike swarms that are the largest conglomerations of matter in the universe, have grown anemically or not at all during the last five billion years, like sullen teenagers who suddenly refuse to eat. “This result could be explained as arrested development of the universe” [The New York Times], said lead researcher Alexey Vikhlinin. He says the findings support the idea that the gravity of the clusters drew in more and more matter for billions of years during their growth spurts. But gravity’s alter ego, dark energy, was tugging at the edges of the clusters, pulling matter away from the galaxies and stalling growth.

Ever since researchers first hypothesized the existence of a mysterious force known as dark energy in the mid-1990s, they’ve scrambled for proof that the force exists, and that it is indeed gradually causing the universe’s expansion to accelerate. Now, Hawaiian astronomers say they have found evidence of dark energy’s work by looking at microwave radiation left over from the Big Bang, and how it acts as it traverses strange regions of the universe.

The findings, which will be published in an upcoming issue of Astrophysical Journal Letters [subscription required], focus on regions of space called superclusters, which are dense with galaxies, and supervoids, which are unusually empty of galaxies. “When a microwave enters a supercluster, it gains some gravitational energy and therefore vibrates slightly faster,” [lead researcher Istvan] Szapudi said. As it leaves the supercluster, he said, “it should lose exactly the amount of energy. “But if dark energy causes the universe to stretch out at a faster rate, the supercluster flattens out in the half-billion years it takes the microwave to cross it,” Szapudi said. “Thus, the wave gets to keep some of the energy as it entered the supercluster” [Honolulu Star-Bulletin].